Electrophotographic image forming apparatuses such as a copier, a printer and a facsimile have been known. These image forming apparatuses form an electrostatic latent image on a surface of a photoreceptor, develop this electrostatic latent image with toner, and transfer and fix the obtained toner image onto a recording medium such as a sheet of paper.
The toner used for developing the electrostatic latent image is supplied from a toner cartridge to a developing device via a toner conveyance path and supplied from the developing device to the surface of the photoreceptor. In a configuration where the toner cartridge is provided above the developing device, a toner conveyance path that extends vertically is provided.
As to a configuration for conveying toner supplied from a toner cartridge to a developing device, for example, a toner replenishment device described in Japanese Laid-Open Patent Publication No. 2012-198368 is provided with a toner receiving port, a feed portion for feeding toner from the toner receiving port into the device, a toner detector for detecting that the device has been filled with a specified amount of the toner, an agitating member that rotates to agitate the toner in the device, a rotational angle detector for detecting a rotational angle of the agitating member, and a recognition portion for recognizing the rotational angle of the agitating member based on output from the rotational angle detector. The toner is fed to the feed portion, when a position of an end edge of an agitating blade included in the agitating member is within a predetermined range not blocking a flow path of the toner from the toner receiving port to the toner detector based on the recognition by the recognition portion. This causes the replenished toner to reach a detector without being blocked by the agitating member, and it is possible to detect quickly and correctly that the toner has been replenished so as to reach a specified amount.
The toner conveyance path that extends vertically is configured as, for example, a conveyance pipe in a pipe shape, and the toner supplied from the toner cartridge passes through the inside of the conveyance pipe in a downward direction and is supplied to the developing device. In this case, the toner is packed inside the conveyance pipe and the conveyance pipe is blocked to impair a conveyance function. For example, in recent years, with improvement in image quality of an image forming apparatus, a particle size of the toner has become finer consequently. Generally, the fine toner has worse fluidity, and the toner is packed more easily in a toner conveyance path of a toner conveyance device.
The toner replenishment device of Japanese Laid-Open Patent Publication No. 2012-198368 is configured as an intermediate hopper for replenishing the toner supplied from the toner cartridge to the developing device, and is provided with the agitating member to agitate the toner for agitating, but the toner is packed in some cases only with the configuration of the agitating member, and a configuration for suppressing packing of the toner effectively is required. Moreover, Japanese Laid-Open Patent Publication No. 2012-198368 is for agitating the toner by the agitating member provided in an almost middle part of the intermediate hopper, and not for effectively preventing packing of the toner in a vicinity of a conveyance screw where packing easily occurs, for example, in a vicinity of a discharge port of the toner.